The present invention relates to an apparatus for the measuring and non-destructive material testing of laid pipelines in the form of a scraper moved through the pipeline and guided on the inner wall thereof and which has at least one circular support with sensors arranged on its circumference and at least one pressure-tight casing, which receives devices for processing and recording the measured values, as well as for the power supply.
Apparatuses of this type, which are also called intelligent scrapers, are increasingly being used in long-distance pipelines, particularly for transporting oil and gas for the purpose of detecting faults on said pipeline. They are generally moved through the pipeline by the medium transported and perform measurements of different types. It is most frequently a question of carrying out measurements on the pipe wall, so as to be able to e.g. establish local corrosion, wall thickness reductions due to mechanical damage, pitting and the like. Differently functioning sensors are used as a function of the intended task, e.g. electrooptical, ultrasonic and similar sensors.
In order to scan the entire circumference of the pipe wall, the sensors are arranged on a rigid ring (U.S. Pat. No. 4,022,055), whereby the ring and, therefore, also the sensors must have a significant distance from the pipe wall, so as not to be damaged by non-circularities of the pipe or local bulges. The measuring accuracy suffers as a result of the significant distance between the effective areas of the sensors and the pipe wall. The measurement result is also falsified in the case of non-circularities and bulges, due to the different type of spacing conditions at the points. In addition, rotary supports for sensors are known (DE-OS No. 2 156 434 and U.S. Pat. No. 3,539,915), but as a result of the rotary movement constitute a source of additional operational problems. Moveover, the sensors are connected by complicated mechanical articulations, linkages, etc to the rotary support, which are intended to ensure that the sensors are guided at a constant distance from the inner wall of the pipe. However, these mechanical means additionally impair the operational reliability. Here again a constant distance between effective sensor area and pipe wall is only ensured to a limited extend. In particular the angulr position of the sensor with respect to the pipe wall, which should always be perpendicular, is not ensured, particularly in the case of non-circularity or other bulges on the pipeline. In addition, a surface-covering scanning is only possible with significant expenditure and effort, if at all, so that in certain circumstances small local defects may not be detected.